The long term goal of this proposed work is to optimize the performance and functionality of SPRINT II with the aim of being better able to study both static and dynamic processes quantitatively. The aim is to extend the capabilities of SPECT to functional imaging. To accomplish this requires improvements in intrinsic detector resolution and linearity, refinement in aperture geometry, more accurate image reconstruction algorithms, and a better understanding of the nature of information transfer in the tomographic imaging process. Detector improvements will be accomplished by means of Monte Carlo modeling and by extending the 1-dimensional maximum likelihood position estimation to 2-dimensions. Optimum aperture design will include a study of mutual information and analysis of variance and bias in reconstructed images. Efficient reconstruction algorithms will be developed for the non-standard sampling geometry of SPRINT II which will include attenuation and scatter correction. Finally, application of mutual information will be extended to detection and discrimination tasks.